This invention generally relates to the field of superconducting ceramics and particularly to manufacturing methods for making superconducting ceramics in a magnetic field and manufacturing apparatuses for the same.
It has long been known that metals such as mercury and lead, intermetallics such as NbNd, Nb.sub.3 Ge and NbGa and ternary materials such as Nb.sub.3 (Al.sub.0.8 Ge.sub.0.2) demonstrate superconductivity. However, the transition temperature, Tc onset, of such long known conventional superconducting materials cannot exceed 25.degree. K.
In more recent years, superconducting ceramics have attracted widespread interest. A new material was first reported by researchers at the Zurich laboratory of IBM Corp. as Ba-La-Cu-O-type high temperature superconducting oxides. Subsequently, La-Sr-Cu(II)-O-type superconducting oxides were also proposed. Other types of superconducting materials have been found in general form YBa.sub.2 Cu.sub.3 O.sub.6-8. It has not been successed hitherto to obtain a superconducting ceramic material having a high Tc higher than 30K by a method in which a mixture of chemicals in a suitable composition is compacted and fired. These superconducting ceramics form a quasi-molecular atomic unit in a perovskite-like structure whose unit cell is constructed with one layer in which electrons have essentially one-dimensional motion, whereas a number of crystalline grains are arranged at randam with diverse crystalline directions, and therefore the critical current density is substantially limited.
Because of this, it is earnestly desired to elevate Tco, the temperature at which resistance vanishes, above the levels previously obtained and preferably above the boiling point of nitrogen (77.degree. K.) or even higher and also to increase critical current densities. In order to solve such shortcomings of prior arts, we have proposed an improved method, as described in our Japanese Patent Application No. sho62-75205 filed on Mar. 27, 1987, entitled "Manufacturing Method of superconducting Materials." The present invention relates to the further improvement and advancement of our previous invention for applying it to methods of making thin films of superconducting oxide materials.